What do the following two equations represent? $-5x-4y = 4$ $12x-15y = 1$
Explanation: Putting the first equation in $y = mx + b$ form gives: $-5x-4y = 4$ $-4y = 5x+4$ $y = -\dfrac{5}{4}x - 1$ Putting the second equation in $y = mx + b$ form gives: $12x-15y = 1$ $-15y = -12x+1$ $y = \dfrac{4}{5}x - \dfrac{1}{15}$ The slopes are negative inverses of each other, so the lines are perpendicular.